Color states with Python's matplotlib/basemap

Question

I want to generate a map of the United States and color each state in using a different shade. Is there a way to do this using Python's basemap?

Answer 1

There is a nicely formated example in the Basemap repo on GitHub: fillstates.py. The shapefile (dbf | shp | shx) is also included in the examples folder.

Here is an abbreviated version of the example:

import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap
from matplotlib.patches import Polygon

# create the map
map = Basemap(llcrnrlon=-119,llcrnrlat=22,urcrnrlon=-64,urcrnrlat=49,
        projection='lcc',lat_1=33,lat_2=45,lon_0=-95)

# load the shapefile, use the name 'states'
map.readshapefile('st99_d00', name='states', drawbounds=True)

# collect the state names from the shapefile attributes so we can
# look up the shape obect for a state by it's name
state_names = []
for shape_dict in map.states_info:
    state_names.append(shape_dict['NAME'])

ax = plt.gca() # get current axes instance

# get Texas and draw the filled polygon
seg = map.states[state_names.index('Texas')]
poly = Polygon(seg, facecolor='red',edgecolor='red')
ax.add_patch(poly)

plt.show()

Resulting plot with Texas filled red:

Note that when we load a shapefile the shapes and attributes are stored in map.states and map.states_info respectively as lists based on the name parameter used in the readshapefile call. So to look up the shape for a specific state we had to build a corresponding list of the state names from the attributes.